Hmmm that does sound very dodgy dude. Either way, you are earning the money inside the UK, therefore should be liable for UK tax and NI. Seems they are trying to use some form of tax avoidance loophole, but I have been out of the tax side of things for a bit. Do you have an accountant for your tax at the moment? If so I would ask them, as from having a quick look, the UKGov are trying to crack down on these types of tax avoidance schemes. I would also look into the legality of them forcing you to go into this scheme, maybe go see citizens advice